1. Field of the Invention
The present invention relates to an article sorting system for sorting during conveyance of an article.
2. Description of the Related Art
Conventionally, various sorting systems have been developed and disclosed in a logistics industry (see, for example Japanese Unexamined Patent Application Publication No. 2009-249121). A sorting system 100 is provided with a plurality of slats (article supporters) 18 on which articles 16 are placed and conveyed, and shoes (article lateral pushers) 20 attached to the slats 18 (FIGS. 14, 15).
The slats 18 are attached to endless chains 14. The endless chains 14 are looped between a drive sprocket 12a and a driven sprocket 12b. A motor is attached to the drive sprocket 12a. The drive sprocket 12a is rotated by the motor, so that the endless chains 14 are rotated.
Each of the slats 18 is directed in an orthogonal direction to the conveying direction of the articles 16. A moving roller 24 and a side roller 26 are provided between the slat 18 and the endless chains 14. When the endless chains 14 are rotated, the moving roller 24 is moved along a slat rail 28. The side roller 26 is guided by a lateral guide surface 30.
Each of the shoes 20 is provided with an upper part 34 on the side of a placement surface 32, a lower part 36 on the opposite side of the upper part, and a side part 38 connecting the upper part 34 and the lower part 36. The shoe 20 is encircling in a sectional view orthogonal to the conveying direction, and is attached so as to encircle part of the slat 18. When each of the articles 16 is placed on the placement surface 32, the shoe 20 is arranged on one of ends of the slat 18. The upper part 34 laterally pushes the article 16. The lower part 36 is used for moving the shoe 20 along the slat 18. A rotation shaft 42 is provided in the lower part 36, and a guide roller 44 is attached to the rotation shaft 42 so as to be freely rotated.
The sorting system 100 is provided with a plurality of branch guide portions 102 in FIG. 16 in order to move the shoe 20. Each of the branch guide portions 102 is provided with forward guide rails 50, a movement guide rail 52, and a distributing means 104. An electromagnet 56 is provided in the distributing means 104. The guide roller 44 is provided with a magnetic body. When the electric power is supplied to the electromagnet 56, the electromagnet 56 attracts the guide roller 44. The guide roller 44 is guided to the movement guide rail 52, so that the shoe 20 is moved along the slat 18. At this time, the shoe 20 laterally pushes the article 16 in the orthogonal direction to the conveying direction. When the article 16 is laterally pushed, the article 16 is moved to a branch conveyor 48.
When the electric power is not supplied to the electromagnet 56, the guide roller 44 goes forward along the forward guide rails 50. The shoe 20 is not moved along the slat 18.
A method for determining a moving distance of the article 16 by a pulse encoder 106 in order to decide whether or not the electric power is supplied to the electromagnet 56 is adopted in JP-A-2009-249121. The pulse encoder 106 is attached to a rotation shaft of the driven sprocket 12b. A moving distance of the endless chains 14 is calculated based on the pulses counted up by the pulse encoder 106. The moving distance of the article is calculated based on the pulses after the article 16 passes through a predetermined position P1. When this calculation obtains a distance indicating that the article 16 reaches a predetermined position P2 of the electromagnet 56, the electric power is supplied to the electromagnet 56 (FIG. 17). The shoe 20 is moved along the slat 18, so that the article 16 is laterally pushed relative to the conveying direction.
However, there is sometimes a case where a calculation result of the moving distance of the article 16 is different from an actual moving distance due to extension of the endless chains 14. Even when correction of the pulses or the like is performed, it is not perfect. When the moving distance of the article 16 cannot be precisely obtained, there is a fear that the article 16 might not be sorted at a predetermined position. By moving the non-predetermined shoe 20, there is sometimes a case where an accident happens.
The shoe 20 is arranged on the end of the slat 18, and moved along the slat 18 when laterally pushing the article 16. For example, supposing that two articles 16b, 16c are conveyed as in FIG. 18(a), and all the shoes 20 are placed on one ends of the slats 18. When the rear article 16c is sorted at first, the shoes 20 which already laterally pushed the article 16c are positioned on the other ends (FIG. 18(b)). Next, the front article 16b is sorted. At this time, the article 16b is directed in an oblique direction relative to the conveying direction, and the article 16b is jut out onto the surrounding slats. When the article 16b is continuously laterally pushed (FIG. 18(c)), the article 16b is nipped by the shoes 20. This may lead to an accident that the article 16b and the shoes 20 are damaged. With consideration for this, an interval between the articles cannot be shortened, so that sorting efficiency for the articles is lowered.
When the calculation result of the moving distance of the article 16 is different from the actual moving distance due to the extension of the endless chains 14, a desired shoe cannot be moved. In order to sort the article 16, there is also a need for reliably moving the desired shoe 20.
Further, when the shoe 20 is damaged, the article 16 cannot be sorted. For example, when the guide roller 44 of the shoe 20 is damaged, the distributing means 104 cannot select the rails 50, 52. When the upper part 34 of the shoe 20 is normal, damage to the shoe 20 cannot be recognized at first glance. Therefore, the damage to the shoe 20 is overlooked, so that the article 16 cannot be sent to the desired branch conveyor 48. Since the article 16 cannot be branched, the article 16 is returned to the upstream side by a rejection conveyor, and the article 16 is sorted again.
When the position of the shoe 20 is not obtained as described above, it takes time to find out the damaged shoe 20, so that restoration takes time. The sorting efficiency for the article 16 is lowered.